I have a Yamaha RX-V2500 receiver and Boston Vrc left,right and center and surround speakers all rated at 8 ohms.I'm have a chance to get some nice Niles ceiling speakers at a great deal, but they are rated at 6 ohms. The receiver has a 6 or 8 ohms setting. If I buy these speakers what setting should i use and how will it effect my Bostons?